Biology subjects

Shrivastav, R.

Publications and source records attributed to Shrivastav, R..

3 recordsLinked to original sources

bioRxiv2025

Aseptic, semi-sealed cranial chamber implants for chronic multi-channel neurochemical and electrophysiological neural recording in nonhuman primates

We developed an implantable neural interface for monitoring both chemical and electrical forms of brain activity in monkeys that maintains aseptic properties for year-long periods while leveraging the modular functions (e.g., sensor moveability) provided by a chamber system. Invasive electrophysiological recordings, especially in subcortical structures from nonhuman primates usually involves implanting electrodes into the brain through a skull-mounted chamber. These electrodes may be attached temporarily for several hours of recording, or permanently. Permanent attachments are favorable to allow for sealing the chamber completely from externally originating pathogenic species that can infiltrate and compromise the health of the animal. A sealed chamber also reduces the need for frequent chamber cleaning required to minimize the accumulation of pathogenic organisms. However, neurochemical measurements require specialized electrodes with extremely fragile carbon fiber tips and are not compatible with recently developed sealed chamber systems. Here, we leveraged osseointegrating materials and hermetic sealing strategies to enable both neurochemical and electrical neural activity measurements from a sealed chamber with an aspirating port for culturing chamber fluid to ensure an aseptic environment. The system was shown to provide successful recordings of neural activity in two monkeys while maintaining negative bacteria culture results for over a year post-implant.

neuroscience↗

bioRxiv2025

Micro-invasive probes for monitoring electrical and chemical neural activity in nonhuman primates

We leveraged carbon fiber materials for creating sensors that provide dual neurochemical and electrical neural activity recording at micro-invasive (10 {micro}m) spatial footprints proximal to recording sites, and enabling these measurements from deep brain targets of primates with conventional cranial chambers. These shaft-assisted micro-invasive probes (s-{micro}IPs) are approximately 10 {micro}m in diameter along the distal length (1 - 15 mm) immediately surrounding the targeted recording site. This micro-invasive portion ensures that the recording site is isolated from tissue damage induced by the wider shaft portion of the device. The shaft (150 - 165 {micro}m in diameter) within the device stiffens the remaining length of the probe (> 100 mm), and provides compatibility with standard intracranial insertion protocols (e.g., guide tubes and chamber setups) that require a sufficiently rigid and long shaft for deep brain insertion in monkeys. The s-{micro}IP was further expanded to provide dual-channel chemical and electrical neural activity recording with micrometer spatial resolution. Measurements of reward- and movement-related dopamine, spikes, and local field potentials were made from single and dual-channel s-{micro}IPs implanted in task-performing monkeys. Recordings from chronically implanted s-{micro}IPs display the capability of functional multi-modal (chemical and electrical) neural activity measurements over 1-year post-implantation from micro-invasive devices.

bioengineering↗

bioRxiv2021

Effects of Task Demands on Neural Correlates of Acoustic and Semantic Processing in Challenging Listening Conditions

PurposeListeners shift their listening strategies to prioritize lower-level acoustic information and higher-level semantic information in challenging listening conditions. However, the neural mechanisms underlying different strategies are unclear. The current study examined the extent to which encoding of lower-level acoustic cues is modulated by task demand and relationships with the higher-level semantic processing. MethodElectroencephalography (EEG) was acquired while participants listened to sentences in noise that contained either higher or lower probability final words. Task difficulty was modulated by time available to process responses. Cortical tracking of speech - neural correlates of acoustic temporal envelope processing - were estimated using temporal response functions (TRFs). ResultsTask difficulty did not affect cortical tracking of temporal envelope of speech under challenging listening conditions. No correlations were observed between the cortical tracking of temporal envelope of speech and semantic processes, even after controlling for the effect of individualized signal-to-noise ratios. ConclusionsCortical tracking of temporal envelope of speech and semantic processing are differentially influenced by task difficulty. While increased task demands modulated higher-level semantic processing, cortical tracking of temporal envelope of speech may be influenced by task difficulty primarily when the demand is manipulated in terms of acoustic properties of the stimulus, consistent with an emerging perspective in speech perception.

neuroscience↗